Catalytic side chain oxidation of aromatic compounds



Patented Mar. 7, 1933 UNITED STATES PATENT; OFFICE ALPHONS O. JAEGEB, FGRAFTON, PENNSYLVANIA, ASSIGNOR TO THE SELDEN COM- IPANY, OF PITTSBURGH,PENNSYLVANIA, A CORPORATION OF DELAWARE CATALYTIC SIDE CHAIN OXIDATIONOF AROMATIC COMPOUNDS No Drawing. Original application filed June 3,1927, Serial No. 196,393. Divided and this application filed March 28,1928. Serial No. 265,521.

phase catalytic oxidations.

It has been proposed in the past to oxidize the side chains of variousaromatic compounds, such as, for example, toluols and substitutedtoluols to benzaldehydes and benzoic acids, xylenes to toluic acids andaldehydes, mesitylene, pseudocumene, and the like to the correspondingacids and aldehydes. Vapor phase oxidation of these products has almostuniformly been unsuccessful for the reaction is very sensitive and tendsto over oxidation resulting in large losses by total combustion and insome cases of the production of undesired by-products. The reaction isstrongly exothermic and when 1t proceeds too far the exotherm is greatlyincreased so that the reaction in the presence of the contact massesused hitherto may be considered to have been in unstable equilibrium andpresents a very serious control problem.

According to the present invention, catalysts or contact massescontaining catalytic elements, whether diluted with carrier particles orundiluted, are associated with stabilizers, which prevent to a largeextent undesired side reactions and permit a catalytic control whichallows excellent yields and high outputs. The stabilizers used in thepresent invention are not to be considered as themselves catalysts. Infact, they are characterized by the fact that they contain basicradicals which in their basicity, valance or stability of their oxidesat high temperatures toward oxidizing agents are radically differentfrom the characteristics of the catalytic elements. The stabilizingelements which are usually present in the form of salts or other activecompounds are the alkali metals, the alkaline earth metals, and someearth metals which form oxides which are not reducible by hydrogen, theprincipal ones being beryllium and magnesium, all of which elements willbe referred to in the present invention as stabilizer forming metals.The salts or other active compounds of these stabilizing elementsproduce a very desirable stabilizing effect, and practically any of thesalts can be used which do not contain acid'radicals having adeleterious effect upon the particular reaction in which the catalyst isto be utilized. Thus, for example, the acid or neutral sulfates,phosphates, halides, chlorates, nitrates, cyanides, both simple andcomplex, arsenates, antimonates, bismuthates, borates, carbonates andthe like give excellent results.

The above compounds are all active chemically, being simple or complexsalts which are ionized. All of these compounds contain the alkaliforming metals in an active form, as opposed to complex silicates of themetals such as certain naturally occurring rocks which, as arewell-known, are inert or practically inert chemically and which arefrequently used as carriers for catalysts. It should be understood thatsuch components are not included under the term active compounds.

The stabilizers can be added to the catalysts or contact massescontaining the catalysts in a chemically preformed state, or they may beproduced by chemical reaction in the presence of the other components ofthe contact mass. Thus, for example, astabilized vanadium pentoxidecatal st may be produced by adding potassium bisulfate in suitableamounts to vanadium oxide in any suitable manner, or a potassiumvanadate catalyst can be caused to react with vapors containing sulfurtrioxide or sulfur dioxide and air, or with dilute sulfuric acid,producing the vanadium oxide and potassium bisulfate in situ. Inbothcases, the potassium bisulfate will act as a stabilizer, .but the actionwill not be the same as the physical.

arrangement of the molecules, and perhaps to a certain extent thechemical combination is different with different methods of producing acontact mass having the same empirical chemical composition, and thecatalytic activity depends not only on the empirical chemicalcomposition, but also on the physical arrangement and on the method offormation of the contact mass. Stabilizers can, of course, also begenerated in situ by reaction of various acid bodies with stabilizerforming metal compounds of components other than the catalyst componentof the contact masses. 7

The stabilizers can be introduced or formed in situ in any desiredmanner, and in the case of diluted catalysts may be incorporated intothe readily formed diluted catalyst, or into a diluent or any of thecatalysts or catalyst forming components before actual formation of thecontact mass.

Another method of producing stabilized catalysts consists inincorporating catalytic components in carriers which themselves containstabilizers or which contain compounds capable of forming stabilizers bysubsequent treatment.

In the catalytic oxidation of side chains of aromatic compounds freealkali is frequently undesirable especially when the oxidation iscarried to the acid stage. Any free alkali present in the contact massescan be readily neutralized by treatment with acid gases as described inmy prior Patent No. 1,678,627 dated July 24, 1928. This treatmenttransforms any alkali present into alkali forming metal salts which actas non-alkaline stabilizers.

Any other suitable method of incorporating compounds of the stabilizerforming metals with catalysts or in contact masses may be used and areincluded in the present invention.

Diluting catalysts with finely divided or highly porous diluents isfrequently desirable, and such diluted catalysts may be associated withstabilizers or stabilizers may be formed therein. It is not definitelyknown whether diluents of desirable physical structure have anyinfluence on the effect of the stabilizers or not, since any efi'ect onthe stabilizer is probably masked by corresponding effects on thecatalyst. Thus, diluents of high orosity or capillarity greatly increasethe e ectiveness of almost any catalyst and naturally, of course,increase the efliciency of any corresponding stabilized catalyst, butwhether this added effectiveness is to be attributed partly to effectson the stabilizer or wholly to effects on the catalyst, is difficult orimpossible to prove and the present invention is not limited toany'theories of action of diluents.

The amount and nature of the stabilizers to be added depends, of course,on the reaction and on the contact mass chosen and especially depends onwhether it is desired to produce aldehydes or acids. In general, alarger amount of stabilizer favors the production of aldehydes.

It is not definitely known just how the stabilizer acts. I am of theopinion, however, that in many, if not most, catalytic oxidations oforganic compounds the most important effect is to reduce its activity intotal combustion. In the case of some vanadium oxide catalysts, thecolor shows that when sufficient stabilizers of suitable type are added,all of the vanadium is not continuously regenerated to vanadiumpentoxide, as the catalyst shows various colors of blue, green and grayand does not remain yellow as is the case with an unstabilized vanadiumoxide catalyst. Whether, however, this is the only effect of astabilizer and whether this effect is true with all catalytic elements,is not difinitely determined and the present invention is not limited toany theory of action and it may well be that the stabilizer has otheractions. It should be noted, however, that while in many cases thestabilizer appears to reduce the oxidation catalytic activity of thecatalyst, it does not reduce the efliciency of the catalyst, but on thecontrary, greatly increases the overall efiiciency, that is to say, theoutput of the desired intermediate oxidation products per unit ofcatalyst per unit of time, and it may be that certain activities of thecatalyst are actually enhanced and in fact this appears likely, becauseas has been stated above, all stabilizing elements are not equallyeffective in their reaction and it may well be that certain stabilizersactually enhance the catalytic power of the catalyst. While it is anadvantage of the present invention that in many cases increased outputsare obtained with stabilized catalysts, the invention is in no senselimited to catalysts or processes in which the actual output isincreased. In some cases, where extreme purity is desired, this can beobtained with a stabilized catalyst by reducing the loading and theadvantages of the present invention can be enjoyed even though theproperties of the catalysts of the present invention are not utilizedall in one direction, namely, increasing the output. As in all catalyticreactions there is a certain compromise between purity of product andoutput, and the best compromise to be chosen in every case will bedetermined by the skilled catalytic chemist.

Stabilized catalysts when used in oxidation reactions according to thepresent invention bring about remarkably improved results, and in manycases a stabilizer alone is sufiicient. I have found, however, that theaddition of other chemical compounds possessing catalytic activity, butnot being specific catalysts for the particular reaction, appears toenhance the effect of the stabilizer and to tune it for more perfectresults for the individual reactions. These compounds will be referredto as stabilizer promoters without thereby limiting the invention to anyparticular theory of action as it may be that the stabilizer promotersdo not act directly on the stabilizer itself. Among the stabilizerpromoters are the usual catalytic compounds containing the usualcatalytic elements and particularly heavy metals and some amphoteri cmetals, such as aluminum, zinc, lead and the like. In general, ofcourse, any catalytic element which is not a specific catalyst for thereaction in question may, when combined with a stabilized catalyst forthat reaction, act as a stabilizer promoter. Among the most effectivestabilizer promoters are, however, some of the catalytic elements whichare by themselves relatively mild catalysts and the effect of thestabilizer promoter is not a pure additive one based on the catal icpower of the elements present in the sta ilizer promoter On thecontrary, the results tend to indlcate that there is a definitecooperation between the stabilizer promoter and the stabilizer catalystsand in some cases, the addition of stabilizer promoters produces resultsgreatly in excess of those which would be predicted from the knowncatalytic power of the promoter elements themselves.

Stabilizer promoters may be added in a chemically preformed state orformed in situ as has been described in the case of stabilizers, and theforms of introduction may take place in any suitable manner, as will beapparent to the skilled chemist. It is, however, by no means necessarythat the stabilizer promoters should be present as separate chemicalcompounds and on the contrary, many very effective catalysts may beproduced by the addition of compounds of the stabilizing forming metalswith various stabilizer promoter elements. Thus. for example, thevarious alkali metal metallates form excellent composite stabilizers andstabilizer promoters. It is possible, of course, that during reactionthese compounds break up to a certain extent, and perhaps even in suchcases the stabilizer becomes completely dissociated from the stabilizerpromoter. It is impossible, however, to determine just what takes placewithin the catalyst during catalysis, and I do not wish to limit myinvention to any theory.

In addition to stabilizers and stabilizer promoters, which are presentor are introduced as individual chemical compounds or combinedchemically with each other, the stabilizer promoters may be present inchemical combination with various diluents. Thus, for example, manyheavy or other metal silicates form at the same time excellent diluentsand stabilizer promoters. Notable examples of these compounds arevarious zeolites in which heavy metal or other elements are present inexchangeable or non-exchangeable form. These zeolites, and, in fact,base exchanging bodies generally, whether zeolites or non-silicious baseexchange bodies, possess for the most part a microporous structure whichis excellently suited as a catalyst diluent or as aframework in or onwhich catalytically active-elements may be hung.

Such base exchange bodies permit in some cases also a chemicalcombination between the stabilizer, stabilizer promoter and the catalystitself. Thus, for example, a zeolite or other base exchange body maycontain a catalytically active element and also a heavy metal or anamphoteric metal oxide associated with stabilizers. Such catalysts areamong the most effective for the oxidation of organic compounds and areof course included as one of the important classes of the presentinvention. The formation of these zeolites or other base exchangebodies, whether containing catalytically active elements in chemicalcombination or not, is described in theco-pending applications of myselfand Johann A. Bertsch, Serial No. 100.116, filed April 6, 1926, andSerial No. 95.771, filed March 18, 1926, and prior Patent No. 1,7 01,-075, dated February 5, 1929, and in my prior Patents No. 1,728,732,dated September 17, 1929, and No. 1,694,620, dated December 11, 1928,and any of the methods of formation therein set forth may be used toproduce base exchange bodies containing stabilizers or stabilizers andstabilizer promoters for use in the side chain oxidation of aromaticcompounds according to the present invention.

The invention is not limited, of course, to the use of any particulardiluent, but diluents of high porosity and high capillarity greatlyenhance the effectiveness of the contact mass used. The action of thediluents, particularly the porous diluents appears to be primarily dueto their physical characteristics. Catalytically active components whichare not catalysts for the particular reaction are classified understabilizer promoters, although. of course, it is diflicult in someextreme cases to draw a line between diluents and stabilizer promotersinthe case of certain compounds which appear to have weak catalyticactivity which may be due to their physical or to their chemicalcharacteristics. In general, however, where components which do notpossess fairly high catalytic activity, as a result of their chemicalstructure, they are to be classed as diluents rather than stabilizerpromoters.

Example 1 200 parts by volume of pea-size pumice fragments areimpregnated with a concentrated solution containing 25 parts by weightof acid potassium phosphovanadate. The contact mass is then dried attemperatures below red heat and calcined and is a good catalyst for theoxidation of toluol, chlorotoluols, nitrotoluols, chlornitrotoluols andbromnitrotoluols to the corresponding aromatic aldehydes and acids.Preferably, Vapors of the compounds should be mixed with a great excessof air and should be passed over the contact mass at 330420 C.

-E:mmple 2 The contact mass thus obtained catalyzes the oxidation oftoluols and substituted toluols, xylienes, pseudocumenes, mesitylene,paracymenc and other substitution products to the correspondingaldehydes and acids under the conditions described above.

E wample 3 30 parts of kieselguhr are mixed with 40 parts of colloidalsilicic acid and then impregnated with 20 parts of potassium molybdate,3 parts of sodium tungstate, 2 parts of lithium tantalate and 30 partsof 33 B. potassium waterglass. The moist mass is pressed into granules,calcined and then given a subsequent short treatment with gasescontaining S0 and chlorine. This contact mass is suited for thecatalytic oxidation of chlortoluol to chlorbenzaldehyde. Instead ofusing gases containing SO and chlorine, gases containing oxides ofnitrogen may be used until no further absorption takes place. A stillfurther tuning of the catalyst may also be effected by the addition of 34 parts of potassium phosphate.

E'azample 4.

12.2 parts of Ta O in the form of potassium tantalate, 10 parts of M00in the form of potassium molybdate, 11.8 parts of W0 in the form ofpotassium tungstate are dissolved in 500 parts of water and suflicient10% sulfuric acid is added with vigorous agitation to precipitate theacids in a finely divided form. 28 parts of U0 in the form of a 5%aqueous solution of uranyl nitrate are then added and uranium hydroxideis precipitated with potassium hydroxide. A solution of 33 B. potassiumwaterglass containing to parts of SiO and diluted with 200 parts ofwater is then added to suspension with vigorous agitation and heated toabout 75 C., the whole solidifying to a gel which on further stirringbreaks up into fragments. These are then sucked as usual, thoroughlywashed in water in a number of portions of about 100 parts each, or thepressed gel can be dried under 109 C. and water permitted to trickleover it until it breaks into fragments.

The product is a zeolite-like body containing in non-exchangeable formtantalum, molybdenum, tungsten and uranium and can be used as a catalystfor the oxidation of toluol and its derivatives to the correspondingaldehydes.

Ewample 5 20 parts of V 0 are suspended in 500 parts of water andacidified with concentrated sulfuric acid and reduced at an elevatedtemperature with gases containing S0 to form the blue vanadyl sulfate.The solution is divided into two equal parts, half being treated with 5Npotassium hydroxide solution at 5060 C. until a clear, coffee-brownsolution of the potassium vanadite is produced, which is then dilutedwith 60 parts of celite or a mixture of 40 parts of celite and 40 partsof finely comminuted quartz. Other diluents such as silicates of theheavy metals or silicates which contain barium, calcium or magnesium ofrocks, tuft, lava, trass, etc. may be used. To this suspension the otherhalf of the vanadyl sulfate solution is added, care being taken thatafter the. addition is complctc, the mixture still reacts alkaline orneutral to phenolphthalein. After freeing from the mother liquor thereaction product is a diluted potassium vanadyl base exchange body whichcan be used for the oxidation of toluol to benzaldehyde. If the alkaliof the base exchange body is neutralized with dilute acids such as forexample, 3 to 5% sulfuric, phosphoric or nitric acids, the neutral oracid alkali metal salt is produced and the resulting contact mass can beused for the catalytic oxidation of toluol to benzoic acid.

E wample 6 A blue vanadyl sulfate solution containing 16.6 parts of V 0is reduced electrolytically between platinum electrodes until the bluecolor of the solution is turned to green, 24 parts of SiO in the form ofa 33 B. waterglass solution are diluted with 10 volumes of water and thevanadium containing solution is stirred in with vigorous agitation untilthe alkalinity is between methyl orange and phenolphthalein red. A lightgreen gelatinous mass precipitates out, which is sucked and dried andconstitutes a zeolite-like body containing trivalent Vanadium oxide innonexchangeable form, and in which the stabilizing alkali is combined ina complex form. This contact mass can be used for the oxidation oftoluol and air to benzaldehyde. Cons derable secondary chemical changestake place in the catalyst during catalysis, as the color undergoesconsiderable change.

This application is a division of my coiending application, Serial No.196,393, filed June 3, 1927, which matured into Patent No. 1,709,853,dated April 23, 1929.

What is claimed as new:

1. A method of oxidizing the side chains of side chain aromaticcompounds, which comprises causing the compounds to react with anoxidizing gas in the presence of an oxidation catalyst having associatedtherewith at least one active compound of a metal included within thegroup of alkali metals, alkaline earth metals.

2. A method of oxidizing the side chains of side chain aromaticcompounds, which comprises causing the vapors of the compounds admixedwith an oxidizing gas to react in the presence of an oxidation contactmass having associated therewith at least one active compound of a metalincluded within the group of alkali metals, alkaline earth metals.

3. A method of oxidizing the side chains of 'side chain aromaticcompounds, which comprises causing the vapors of the compounds admixedwith an oxidizing gas to react in the presence of an oxidation contactmass having associated therewith at least one active compound of a metalincluded within the group of alkali metals. alkaline earth metals and atleast one catalyst included in the group consisting of hydrogenationcatalysts,

' dehydrogenation catalysts, reduction catalysts, oxidation catalystswhich, when used alone, are not specific catalysts for the oxidation ofside chain aromatic compounds, the catalytic activity of the specificcatalysts for the side chain oxidation of aromatic compounds containedin the oxidation contact mass being greater than that of thenon-specific catalysts included in the above 4. A method of oxidizingthe side chains of side chain aromatic compounds, which comprisescausing the vapors of the compounds admixed with an oxidizing gas toreact in the presence of an oxidation contact mass having associatedtherewith at least one active compound of a metal included within thegroup of alkali metals, alkaline earth metals and also containing anoxygen compound of vanadium as at least one of its catalytically activecomponents.

5. A method of oxidizing the side chains of side chain aromaticcompounds, which comprises causing the Vapors of the compounds admixedwith an oxidizing gas to react in the presence of an oxidation contactmass having associated therewith at least one non-alkaline activecompound of a metal included within the group of alkali metals, alkalineearth metals.

6. A method of oxidizing the side chains of benzene homologue compounds,which comprises causing them to react with oxidizing gas in the presenceof an oxidation catalyst having associated therewith at least one activecompound of a metal included within the agroup of alkali metals,alkaline earth met s.

7. A method of oxidizing the side chains of benzene homologue compounds,which comprises causing the vapors of the compound to react with anoxidizing gas in the presence of an oxidation contact mass havingassociated therewith at least one active compound of a metal includedwithin the group of alkali metals, alkaline earth metals.

8. A method of oxidizing the side chains.

of benzene homologue compounds, which comprises causing the vapors ofthe compound to react with an oxidizing gas in the presence of anoxidation contact mass having associated therewith at least one activecompound of a metal included within the group of alkali metals, alkalineearth metals and at least one catalyst included in the group consistingof hydrogenation catalysts, dehydrogenation catalysts, reductioncatalysts, oxidation catalysts which, when used alone, are not specificcatalysts for the oxidation of side chain aromatic compounds, thecatalytic activity of the specific catalysts for the side chainoxidation of aromatic compounds contained in the oxidation contact massbeing greater than that of the nonspecific catalysts included in theabove group.

9. A method of oxidizing the side chains of benzene homologue compounds,which comprises causing the vapors of the compound to react with anoxidizing gas in the presence of an oxidation contact mass havingassociated therewith at least one active compound of a metal includedwithin the group of alkali metals, alkaline earth metals and alsocontaining an oxygen compound of vanadium as at least one of itscatalytically active components.

10. A method of oxidizing the methyl group of benzene homologuecompounds containing at least one methyl group, which comprises causingthe compound to react with an oxidizing gas in the presence of anoxidation catalyst having associated therewith at least one activecompound of a metal included within the group of alkali metals, alkalineearth metals.

11. A method of oxidizing the methyl groups of benzene compoundscontaining at least one methyl group, which comprises causing the vaporsof the compounds to react with an oxidizing gas in the presence of anoxidation contact mass having associated therewith at least one activecompound of a metal included within the group of alkali metals, alkalineearth metals.

12. A method --of oxidizing the methyl groups of benzene compoundscontaining at least one methyl group, which comprlses causing the vaporsof the compounds to react with an oxidizing gas in the presence of anoxidation contact mass having associated therewith at least one activecompound of a metal included within the group of alkali metals, alkalineearth metals and at least one catalyst included in the group consistingof hydrogenation catalysts, dehydrogenation catalysts, reductioncatalysts, oxidation cata lysts which, when used alone, are not specificcatalysts for the oxidation of side chain aromatic compounds, thecatalytic activity of the specific catalysts for the side chainoxidation of aromatic compounds contained in the oxidation contact massbeing greater than that of the non-specific catalysts included in theabove group.

13. A method of oxidizing the methyl groups of benzene compoundscontaining at least one methyl group, which comprises causing the vaporsof the compound to react with an oxidizing gas in the presence of anoxidation contact mass having associated therewith at least one activecompound of a metal included within the group of alkali metals, alkalineearth metals and also containing an oxygen compound of vanadium as atleast one of its catalytically active components.

14. A method of oxidizing side chains of toluene compounds whichcomprises causing vapors of the compounds admixed with an oxidizing gasto react in the presence of an oxidation contact mass having associatedtherewith at least one active component of a metal included within thegroup of alkali metals, alkaline earth metals.

15. A method of oxidizing side chains of toluene compounds whichcomprises causing vapors of the compounds admixed with an oxidizing gasto react in the presence of an oxidation contact mass having associatedtherewith at least one active compound of a metal included within thegroup of alkali metals, alkaline earth metals and at least one catalystincluded in the group consisting of hydrogenation catalysts,dehydrogenation catalysts, reduction catalysts, oxidation catalystswhich, when used alone, are not specific catalysts for the oxidation ofside chain aromatic compounds, the catalytic activity of the specificcatalysts for the side chain oxidation of aromatic compounds containedin the oxidation contact mass being greater than that of thenon-specific catalysts included in the above group.

16. A method of oxidizing side chains of toluene compounds whichcomprises causing vapors of the compounds admixed with an oxidizing gasto react in the presence of an oxidation contact mass having associatedtherewith at least one active compound of a metal included within thegroup of alkali metals, alkaline earth metals and also containing anoxygen compound of vanadium as one of its catalytically activecomponents.

17. A method of oxidizing a side chain of toluene which comprisescausing it to react with an oxidizing gas in the presence of anoxidation catalyst containing at least one active compound of a metalincluded with the group of alkali metals, alkaline earth metals.

18. A method of oxidizing a side chain of toluene which comprisescausing the vapors of toluene admixed with an oxidizing gas to react inthe presence of an oxidation contact mass having associated therewith atleast one active compound of a metal included with the group of alkalimetals, alkaline earth metals.

19. A method of oxidizing a side chain of toluene which comprisescausing the vapors of toluene admixed with an oxidizing'gas to react inthe presence of an oxidation contact mass having associated therewith atleast one active compound of a metal included within the group of alkalimetals, alkaline earth metals and at least one catalyst included in thegroup consisting of hydrogenation catalysts, dehydrogenation catalysts,reduction catalysts, oxidation catalysts which, when used alone, are notspecific catalysts for the oxidation of side chain aromatic compounds,the catalytic activity of the specific catalysts for the side chainoxidation of aromatic compounds contained in the oxidation contact massbeing greater than that of the non-specific catalysts included in theabove group.

20. A method of oxidizing a side chain of toluene which comprisescausing the vapors of toluene admixed with an oxidizing gas to react inthe presence of an oxidation contact mass having associated therewith atleast one active compound of a metal included with the group of alkalimetals, alkaline earth metals, the contact mass also containing anoxygen compound of vanadium as at least one of its catalytically activecomponents.

Signed at Pittsburgh, Pennsylvania, this 23rd day of March, 1928.

ALPHONS O. JAEGER.

